1. Field of the Invention
The present invention relates to a signal cable for connecting electronic machines, and more specifically, to a signal cable in which the shape of a shield can (a so-called steel cap) built inside a connector is improved, and a cylindrical ferrite core is built inside the connector.
2. Description of the Related Art
In general, a conventional signal cable is constructed in a manner shown in FIG. 2. That is, a pin to which an insulator 30 and a core wire 40 are connected is built inside a metallic shell 20, a shield can composed of an upper cap 50 and a lower cap 60 is attached to the rear side of the metallic shell 20, and a hood 70 covers the shield can.
However, when the shield can is divided into the upper and lower caps, a variety of processes should be performed for reliable shielding. For example, the shield can is wrapped with paper, a copper tape is wound around the shield can a plurality of times, and soldering is performed to close a minute gap between layers of the wound tape.
In particular, since the soldering is performed in a state where the core wire is present, various defects may occur. For example, the core wire may be short-circuited by heat caused by the soldering. Further, since a variety of unnecessary and complicated processes should be carried out, productivity decreases, and a manufacturing cost increases.
Meanwhile, a ferrite core is attached to the connector of the signal cable, in order to block unnecessary electromagnetic waves flowing in from outside. In the related art, a ferrite core 80 is inserted into the outside of the cable, and an outer circumferential surface (outer shell) of the ferrite core 80 is fixed and bonded by PVC, as shown in FIG. 1. Therefore, the appearance of the signal cable is degraded. Further, when an electronic machine such as a computer is installed, the cable is connected to the rear of the computer. In this case, since the cable is not smoothly curved because of the cylindrical ferrite core mounted on the cable, a predetermined space should be secured behind the computer.
That is, to connect the core wire 40 to the pin 90, various insulation coverings such as braiding, aluminum foil and the like, which cover the core wire 40, should be all peeled off. The peeled portion of the core wire 40 does not contribute to blocking harmful electromagnetic waves.
Therefore, as the ferrite core for blocking harmful electromagnetic waves is positioned adjacent to the peeled portion of the core wire, the shielding effect increases.
However, if the ferrite core 80 is attached immediately behind the connector so as to be positioned adjacent to the connector, and when an electronic machine is installed, the cable is not smoothly curved because of the cylindrical ferrite core mounted on the cable. Therefore, a predetermined space should be secured behind the electronic machine.
To solve such a problem, the present applicant has disclosed a D-sub connector having a ferrite core built therein (Korean Utility Model Patent No. 102248), in which a ferrite core is built inside a D-sub metallic shell. The workability thereof is excellent, compared with when the cylindrical ferrite core is attached to the conventional cable. However, an additional operation is required for mounting the ferrite core into the metallic shell, and the size of the ferrite core is inevitably reduced. Therefore, it is difficult to expect the maximum effect.